Summary - Labels

Combine labels and selectors to group and filter resources.

Summary: Labels

In this group:

Labels are selectable key-values; annotations are non-selectable extra info.
kubectl label adds, --overwrite changes, key- removes; annotate works with the same syntax.
Selectors: matchLabels (equality) and matchExpressions (In, NotIn, Exists, DoesNotExist); a Deployment selector is immutable.
-l filters (comma = AND), -L adds columns; bulk deletes, logs and restarts are done with selectors.
Set expressions are quoted: -l 'ortam in (prod,staging)'.

kubectl label pods -l app=web surum=v2
kubectl get pods -l 'surum in (v1,v2)' -L surum

Exercise Recommended labels

Write a Deployment template's metadata section (starting with metadata:): under labels, app.kubernetes.io/name: web, app.kubernetes.io/version: "1.4.2", app.kubernetes.io/part-of: magaza; under annotations, aciklama: "ana sayfa servisi".

Show example solution

metadata:
  labels:
    app.kubernetes.io/name: web
    app.kubernetes.io/version: "1.4.2"
    app.kubernetes.io/part-of: magaza
  annotations:
    aciklama: "ana sayfa servisi"

Test yourself

Why isn't a version label put in a Deployment selector?
- The selector is immutable; when the version changes, the deployment would have to be recreated
- Version labels are forbidden
- The Service can't see it
- The label is too long
Show answer

The selector is immutable; when the version changes, the deployment would have to be recreated — The version goes in the template label, not the selector.

Add a new label to all pods that have a label.

kubectl label pods ____ app=web surum=v2

Show answer

kubectl label pods -l app=web surum=v2

Match.

label

For selection
annotation

For information
-l

Filter
-L

Column

Next lesson: Project design

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